linux-kernel - Re: [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus

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Date:   Wed, 2 Jun 2021 13:08:13 -0500
From:   Rob Herring <robh@...nel.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Thierry Reding <treding@...dia.com>,
        dri-devel@...ts.freedesktop.org,
        Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>,
        Stephen Boyd <swboyd@...omium.org>, robdclark@...omium.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Steev Klimaszewski <steev@...i.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonas Karlman <jonas@...boo.se>, Lyude Paul <lyude@...hat.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Linus W <linus.walleij@...aro.org>,
        linux-arm-msm@...r.kernel.org,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Rob Herring <robh+dt@...nel.org>,
        Andrzej Hajda <a.hajda@...sung.com>
Subject: Re: [PATCH v8 02/11] dt-bindings: drm: Introduce the DP AUX bus

On Mon, 24 May 2021 17:01:50 -0700, Douglas Anderson wrote:
> We want to be able to list an eDP panel as a child of an eDP
> controller node to represent the fact that the panel is connected to
> the controller's DP AUX bus. Though the panel and the controller are
> connected in several ways, the DP AUX bus is the primary control
> interface between the two and thus makes the most sense to model in
> device tree hierarchy.
> 
> Listing a panel in this way makes it possible for the panel driver to
> easily get access to the DP AUX bus that it resides on, which can be
> useful to help in auto-detecting the panel and for turning on various
> bits.
> 
> NOTE: historically eDP panels were _not_ listed under their controller
> but were listed at the top level of the device tree. This will still
> be supported for backward compatibility (and while DP controller
> drivers are adapted to support the new DT syntax) but should be
> considered deprecated since there is no downside to listing the panel
> under the controller.
> 
> For now, the DP AUX bus bindings will only support an eDP panel
> underneath. It's possible it could be extended to allow having a DP
> connector under it in the future.
> 
> The idea for this bus's design was hashed out over IRC [1].
> 
> [1] https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&date=2021-05-11
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> My DT yaml-fu is still weak. If I did something stupid, please help me
> learn how to do this better!
> 
> NOTE: there is no "Example" in this bindings file. Yikes! This is
> because I wanted to keep this patch separate from the one that enables
> the first eDP controller. See the patch ("dt-bindings: drm/aux-bus:
> Add an example") for the example.
> 
> ALSO: if anyone else would like to be listed as a "Maintainer" in this
> file then please shout!
> 
> Changes in v8:
> - Separate DP AUX bus binding is new for v8.
> 
>  .../bindings/display/dp-aux-bus.yaml          | 37 +++++++++++++++++++
>  1 file changed, 37 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/dp-aux-bus.yaml
> 

Reviewed-by: Rob Herring <robh@...nel.org>